What to Do If You Find Your Furnace Leaking Water in Winter

While many people are familiar with an air conditioner leaking water during summer, a furnace leaking water in winter may seem less common. However, in homes with high-efficiency furnaces (units with an efficiency rating of 90% or above), water leakage is a potential issue. Here’s why you may find furnace leaking water in winter and how to deal with it.

Where the Water Comes From and Where It Goes

A high-efficiency furnace is so effective because it utilizes a secondary heat exchanger. This component extracts extra heat by condensing the flow of furnace exhaust gases. The process produces condensation in the form of slightly acidic water. In daily usage, a typical residential high-efficiency furnace can produce about 5 gallons of condensation. This water is routed through a one-way trap that prevents hazardous gases such as carbon monoxide from entering the house. The flow of condensate is then routed through a PVC pipe that drains outside the house or into a floor drain. An electric pump may be installed to propel the condensate flow.

How Leaks Happen

A furnace leaking water in winter can result from three issues:

• Blockage in the trap. If a clog occurs in the condensate drain trap, water will back up into the furnace.  It may spill into the interior of the furnace and out onto the floor, forming puddles. Alternatively, a safety sensor that detects condensate blockage will automatically shut down the furnace.
• Leakage in the drainage system. Leaks may occur in the PVC drain pipe itself or at fittings that connect segments of pipe. Also, if the system is fitted with a condensate pump, leaks may originate in the pump.
• Outdoor ice. Freezing temperatures may cause ice to form at the outdoor end of the drain pipe. This may obstruct drainage flow and trigger a backup that ultimately causes leakage (or an automatic shutdown) at the furnace.

What You Can Do

Condensate clogs or leakage may involve critical safety issues such as dangerous combustion gasses. For this reason, resolving furnace-condensate problems should be left to certified, professional heating technicians only.

To diagnose and resolve a furnace leaking water in winter, contact Energy 1 Heating & Air Conditioning.